Seat back release

I just purchased this truck used. It is the extended cab with the 40/20/40 front seat configuration. Both the seat back levers were missing. I picked up two levers from a salvage yard but when I went to put them on it looks like 1) either the remnants of old lever center is still there, or 2) the splines have been rounded off? Is the shaft that accepts these levers made of plastic or steel?